Secretary of State John Kerry sets out this week to convince Congress that it should not place new roadblocks in the way of a two-step plan that world powers are trying to conclude with Iran over its nuclear program.

But Secretary Kerry’s task is not an easy one: France, one of the parties to the negotiations with Iran, has called the plan “a fool’s game” that leaves Iran too much leeway to pursue its nuclear ambitions. And Israel has exhorted American Jewish groups to pressure Congress to do what it can to discourage US support for an interim agreement.

The first step of this plan would basically curtail some of Iran’s nuclear activity in exchange for some reversible relief from harsh economic sanctions – but would leave the building blocks of both Iran’s nuclear program and the international sanctions in place. Negotiators would then have six months to work out a comprehensive deal to verifiably block Iran’s path to a nuclear weapon in exchange for a lifting of the international sanctions ravaging Iran’s economy.

Yet if anything, Congress wants to ramp up sanctions, not soften them at this point, asserting that only more economic hardship can persuade Iran to shut down and dismantle its nuclear program.

The deep skepticism that Kerry can expect to encounter among members of Congress was on display when Tennessee Sen. Bob Corker, the top Republican on the Foreign Relations Committee, said on NBC’s “Meet the Press” Sunday that he feared the administration was “going to deal away the leverage that we have” with Iran.

Using a cautionary comparison that has become a staple of critics of a phased-in agreement with Iran, Senator Corker said, “A partial agreement leads us down the same path we went down with North Korea.”

Over a two-decade period, North Korea agreed to plans and in some cases took steps toward ending its nuclear program. But it later disavowed the agreements. In February, it announced it had conducted its third nuclear test in recent years.

Kerry will also find that concern over the proposed first-step partial agreement is far from a Republican monopoly. New York Rep. Eliot Engel, the highest-ranking Democrat on the House Foreign Affairs Committee, said in a statement Friday he is “deeply troubled” that the initial agreement would call for Iran to take some immediate steps to curtail its nuclear activities – but not to halt all uranium enrichment, for example.

Saying he wants any first step to achieve “much more,” Representative Engel noted that United Nations Security Council resolutions demand a halt to Iran’s enrichment activities.

Highly enriched uranium is one means of fueling a nuclear bomb. Iran is not known to have created highly enriched uranium, but it is stockpiling lower levels of enriched uranium that could eventually be purified to weapons-grade uranium.

High-ranking officials from six world powers – the United States, China, Russia, Britain, France, and Germany – met with Iranian officials in Geneva last week and appeared by Sunday morning to have come tantalizingly close to reaching a deal that has eluded the international community for the past decade.

But last-minute balking on both sides put off any deal-signing, although the parties agreed to try again with a fresh round of talks Nov. 20.

Speaking Monday in Abu Dhabi in the United Arab Emirates before returning to Washington, Kerry played down reports of disunity among the international powers, claiming it is the Iranians who “weren’t able to accept” the deal on the table Sunday morning.

“The French signed off on it, we signed off on it, and everybody agreed it was a fair proposal,” he said.

In Paris, Foreign Minister Laurent Fabius – who like Kerry was in Geneva for the talks but balked at the plan – said on French radio that “there are several issues that still need to be discussed” before any deal can be reached. Minimizing reports that it was France that scuttled the interim accord, Mr. Fabius said, “We are not far from an agreement with the Iranians, but we are not there yet.”

Among the issues Fabius said were not sufficiently addressed is Iran’s stockpile of 20 percent enriched uranium – a level just a few steps shy of the highly enriched uranium that can fuel a bomb.

In addition, the accord would have to address the looming completion of a heavy-water reactor in Arak, Iran, he said. If operational as planned at the end of 2014, the Arak plant would churn out spent fuel containing plutonium – another potential bomb fuel. “We have to make arrangements for this reactor in Arak not to be activated as planned,” Fabius said.

Despite those concerns, senior US officials insisting on anonymity to discuss the negotiations said Iran’s insistence that an accord enshrine its “right” to uranium enrichment is what torpedoed an agreement Sunday.

While pressure is likely to grow to stop any short-term confidence-building measures with Iran, Kerry can also take the Obama administration’s position to Congress knowing that no action could be taken before the next round of talks Nov. 20, supporters of the administration’s approach say.

“The debate about Iran negotiations will intensify, [and] many members of Congress will raise the political heat on the administration to shift its negotiating position as a result of the delay in cementing a confidence-building deal,” says Joel Rubin, director of policy and government affairs at the Ploughshares Fund, an organization promoting nuclear nonproliferation.

But “the legislative facts will not change, [and] no new sanctions bill between now and Nov. 20 will become law,” Mr. Rubin notes. What the administration can do, he adds, is “remind Congress that there’s no need for additional pressures, as a lack of pressure wasn’t the issue in these talks.”